UV sources are needed for detecting biologically active molecules through fluorescence when labelled by a chromophore. However, the best 350 nm source, the Argon-ion laser, is incompatible with a table-top instrument since it requires installing permanent support utilities. This constraint has prevented the clinical use of techniques such as DNA sorting which would help determine treatment strategies for cancer patients, and it has limited researchers in problems such as AIDS research which require semi- clinical data. This project will develop a diode laser based UV light source which makes possible a table-top UV flow cytometer. In Phase I, we will build a UV source to demonstrate the new optics technology required for success. This will be the first diode-laser UV source. We will also work with our collaborators at Stanford University and Los Alamos National Laboratory to identify methods to evaluate a cytometer based on this source. In Phase II, we will construct prototypes, install them into our collaborators' cytometry machines, and begin experiments to demonstrate the system performance. In Phase III, we will work with a manufacturer to develop a commercial table-top diode-based multi-wavelength cytometry system.